Why can't we send stone models?

Stone models don't always survive the shipping process. There is usually some sort of chipping, especially along the cusps/incisal edges. Sometimes this can be a whole tooth, but most of the time it will be something minor that's hard to detect but can still affect the fit of the aligners.

Also, with stone models, we can't control the quality of the stone model. The impression might be perfect, but if the pour-up is bad the scan will be compromised. Things like air bubbles can be filled in, but it leaves us guessing at what the shape of the tooth is actually like.

Bite registrations are not required to submit your case because our software automatically articulates the arches in maximum intercuspation. For the vast majority of cases, this is as accurate as (or more accurate than) aligning models based on a bite registration. Our technicians also double-check the occlusion against the photos you provide.

Bite registrations will not be scanned unless specifically requested (either in the prescription form or in response to the technician in a setup decline).

When taking impressions, I have difficulty getting the distal of the last molars. Do you have any suggestions on an easy way to capture these?

Posterior distortion of the most distal teeth in the arch is 3rd on the list of most common impression issues. It can be difficult to get a good impression since it's hard to see back there. There are a couple of ways to avoid this problem:

Make sure that you're using a correctly-sized tray. It should extend past the last tooth in the arch without touching the gums.

Before inserting the tray containing light body, add some light body directly to the occlusal and distal portion of the last tooth in the arch, ensuring that the last tooth is completely covered with impression material.